This invention relates to a method of increasing the width of a band of voltages associated with a particular identification code as the voltages themselves increase.
The present invention is specifically directed to a disclosed system wherein an identification voltage is associated with particular types of fuel injectors to provide a control feedback on characteristics of those fuel injectors. A series of distinct voltages are associated with different combinations of two characteristics. The control can read an electric signal which is influenced by the voltages, and can thus identify the particular combination of characteristics. One problem with this type of system is the reduction or elimination of identification errors. Thus, it would be desirable to minimize the occurrences of when a particular monitored voltage is associated with a particular set of characteristics by the control, but wherein the injector actually possesses a different set of characteristics than that which the control has identified.
A number of different factors can influence the occurrence of such errors. As an example, a disclosed embodiment utilizes resistors to provide the coding identification voltages. Of course, as with any manufactured items, there are tolerances within the resistors. Thus, the resistors themselves can result in errors in the voltage. Moreover, the voltage source which drives the entire system may also vary from the predicted voltage source values, which can also result in errors.
It is has been found that when errors in the voltage source occur, the errors are effectively almost proportional to the voltage. Further, when the errors are due to an error in the resistance in the resistors being utilized to provide the identification voltage, the error is almost proportional to the voltage.
As the voltages associated with codes increase, and as the number of codes themselves increase, the possible errors thus also increase. As the possible error increases, the likelihood of a misreading error also increases if the differences between the voltage associated with adjacent codes are equally spaced.
While the invention is disclosed with regard to voltage identification of codes for use in identifying characteristics of fuel injectors, any system which utilizes an increasing voltage as an identification code for particular characteristics can benefit from this invention. In fact, any system which has an increasing variable for identifying a plurality of codes, be it voltage or some other variable, will benefit from this invention.
In the disclosed embodiment of this invention, an identification voltage is associated with a number of systems. Distinct identification voltages are identified with distinct combinations of characteristics for each of a plurality of types of systems. The distance between adjacent voltages, and the associated band between minimum and maximum for each of the codes increase as the voltage itself increases. In this way, with increasing voltage the possible error will increase, but since the band or distance between the adjacent codes also increases, the likelihood of a reading error is maintained small.
In a disclosed embodiment, the codes are associated with a pair of characteristics with regard to fuel injectors. However, the identification voltages can be associated with other types of systems. Further, the invention would also extend to coding variables other than voltage.
In a preferred embodiment, a value for the center of each of the identification values is first determined. Preferably, a value at the center of the uppermost bin and the lowermost bin are first selected. In a disclosed embodiment, the value of voltage at the center of the uppermost bin is 4.0 volts and the value at the lower most bin center is 1.0 volts. A quotient is then determined by dividing these two values. In a most preferred embodiment the log of this quotient is taken. Either a common or a natural log may be used. The log of the quotient is then divided by the number of desired bins minus one. The antilog is then taken. The antilog is then utilized to scale up the value of each of the centers of each of the identification codes. To determine boundaries between each of the codes a second factor may be calculated by taking the square root of the antilog factor. The lower limit is found by dividing the value of the center of the bin of each of the coding values by this second factor. The upper limit is found by multiplying the value at the center of the bin by this second factor. In this way, the bins or identification codes are proportionally spaced.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.